O movimento funcional de alcance em uma abordagem ecológica

Teorias de controle motor tradicionais assumiam um modelo de representação interna responsável pela organização e regulação do alcance, tendo por controlador o sistema nervoso central (SNC). Perspectivas contemporâneas questionam a habilidade de somente o SNC controlar e regular os movimentos. Ações podem não ser guiadas apenas pelo SNC, mas também por informações presentes no ambiente, estando o controle no sistema indivíduo-ambiente. A detecção da informação é um processo ativo: o indivíduo explora o ambiente, percebe possibilidades de ação fornecidas por ele e age em reposta ao que é oferecido. O objetivo deste estudo foi descrever o desenvolvimento e a coordenação do alcance em uma perspectiva teórica fundamentada na abordagem ecológica à percepção-ação, para promover melhor compreensão do movimento humano. Discutem-se nesta revisão de literatura o desenvolvimento do alcance desde a infância até a idade adulta, formas de operacionalização, fatores extrínsecos e intrínsecos relacionados, relações invariantes entre indivíduo e objeto a ser alcançado. Esse referencial teórico pode permitir a compreensão de como intervenções alteram a estabilidade vigente no sistema, levando à emergência de novas soluções funcionais. Em uma visão ecológica, o alcance é entendido de forma ampla: para explicar a ocorrência do movimento, devem considerar-se as informações do ambiente, além das características intrínsecas do indivíduo.Traditional motor control theories rely on a model of internal representation responsible for the organization and regulation of reaching movements, controlled by the central nervous system (CNS). Contemporary perspectives argue the ability of the CNS alone to control and regulate voluntary movements, since actions may also be guided by environmental information, wherein control would be exerted by the individual-environment system. The detection of information is an active process: subjects explore the environment, perceive possibilities of action, and act in response to the environment. The purpose of this study is to describe development and coordination of reaching movements from a theoretical perspective based on an ecological approach to perception-action, in order to provide better understanding of human movement. This literature review discusses the development of reaching movements from infants to adults, operational functions, related extrinsic and intrinsic factors, and invariant relations between the subject and the target object. This theoretical framework allows for a better understanding on how interventions may alter system stability, leading to the emergency of new functional solutions. In an ecological approach, reaching is understood in a broad way: in order to explain movement, environment information is considered, besides subjects' intrinsic characteristics

Synchrony of hand-foot coupled movements: is it attained by mutual feedback entrainment or by independent linkage of each limb to a common rhythm generator?

BACKGROUND: Synchrony of coupled oscillations of ipsilateral hand and foot may be achieved by controlling the interlimb phase difference through a crossed kinaesthetic feedback between the two limbs, or by an independent linkage of each limb cycle to a common clock signal. These alternative models may be experimentally challenged by comparing the behaviour of the two limbs when they oscillate following an external time giver, either alone or coupled together. RESULTS: Ten subjects oscillated their right hand and foot both alone and coupled (iso- or antidirectionally), paced by a metronome. Wrist and ankle angular position and Electromyograms (EMG) from the respective flexor and extensor muscles were recorded. Three phase delays were measured: i) the clk-mov delay, between the clock (metronome beat) and the oscillation peak; ii) the neur (neural) delay, between the clock and the motoneurone excitatory input, as inferred from the EMG onset; and iii) the mech (mechanical) delay between the EMG onset and the corresponding point of the limb oscillation. During uncoupled oscillations (0.4 Hz to 3.0 Hz), the mech delay increased from -7° to -111° (hand) and from -4° to -83° (foot). In contrast, the clk-mov delay remained constant and close to zero in either limb since a progressive advance of the motoneurone activation on the pacing beat (neur advance) compensated for the increasing mech delay. Adding an inertial load to either extremity induced a frequency dependent increase of the limb mechanical delay that could not be completely compensated by the increase of the neural phase advance, resulting in a frequency dependent increment of clk-mov delay of the hampered limb. When limb oscillations were iso- or antidirectionally coupled, either in the loaded or unloaded condition, the three delays did not significantly change with respect to values measured when limbs were moved separately. CONCLUSION: The absence of any significant effect of limb coupling on the measured delays suggests that during hand-foot oscillations, both iso- and antidirectionally coupled, each limb is synchronised to the common rhythm generator by a "private" position control, with no need for a crossed feedback interaction between limbs

Aging affects attunement in perceiving length by dynamic touch

Earlier studies have revealed age-dependent differences in perception by dynamic touch. In the present study, we examined whether the capacity to learn deteriorates with aging. Adopting an ecological approach to learning, the authors examined the process of attunement—that is, the changes in what informational variable is exploited. Young and elderly adults were trained to perceive the lengths of unseen, handheld rods. It was found that the capacity to attune declines with aging: Contrary to the young adults, the elderly proved unsuccessful in learning to detect the specifying informational variables. The fact that aging affects the capacity to attune sets a new line of research in the study of perception and perceptual-motor skills of elderly. The authors discuss the implications of their findings for the ongoing discussions on the ecological approach to learning

Parkour as a donor sport for athletic development in youth team sports: insights through an ecological dynamics lens

Analyses of talent development in sport have identified that skill can be enhanced through early and continued involvement in donor sports which share affordances (opportunities for action) with a performer's main target sport. Aligning key ideas of the Athletic Skills Model and ecological dynamics theory, we propose how the sport of parkour could provide a representative and adaptive platform for developing athletic skill (e.g. coordination, timing, balance, agility, spatial awareness and muscular strength). We discuss how youth sport development programmes could be (re) designed to include parkour-style activities, in order to develop general athletic skills in affordance-rich environments. It is proposed that team sports development programmes could particularly benefit from parkour-style training since it is exploratory and adaptive nature shapes utilisation of affordances for innovative and autonomous performance by athletes. Early introduction to varied, relevant activities for development of athleticism and skill, in a diversified training programme, would provide impetus for a fundamental shift away from the early specialisation approach favoured by traditional theories of skill acquisition and expertise in sport

Three People Can Synchronize as Coupled Oscillators during Sports Activities

We experimentally investigated the synchronized patterns of three people during sports activities and found that the activity corresponded to spatiotemporal patterns in rings of coupled biological oscillators derived from symmetric Hopf bifurcation theory, which is based on group theory. This theory can provide catalogs of possible generic spatiotemporal patterns irrespective of their internal models. Instead, they are simply based on the geometrical symmetries of the systems. We predicted the synchronization patterns of rings of three coupled oscillators as trajectories on the phase plane. The interactions among three people during a 3 vs. 1 ball possession task were plotted on the phase plane. We then demonstrated that two patterns conformed to two of the three patterns predicted by the theory. One of these patterns was a rotation pattern (R) in which phase differences between adjacent oscillators were almost 2π/3. The other was a partial anti-phase pattern (PA) in which the two oscillators were anti-phase and the third oscillator frequency was dead. These results suggested that symmetric Hopf bifurcation theory could be used to understand synchronization phenomena among three people who communicate via perceptual information, not just physically connected systems such as slime molds, chemical reactions, and animal gaits. In addition, the skill level in human synchronization may play the role of the bifurcation parameter

Joint angle variability and co-variation in a reaching with a rod task

The problem at the heart of motor control is how the myriad units of the neuromotor system are coordinated to perform goal-directed movements. Although for long these numerous degrees of freedom (DOFs) were considered redundant, recent views emphasize more that the DOFs should be considered abundant, allowing flexible performance. We studied how variability in arm joints was employed to stabilize the displaced end-effector in tool use to examine how the neuromotor system flexibly exploits DOFs in the upper extremity. Participants made pointing movements with the index finger and with the index finger extended by rods of 10, 20, and 30 cm. Using the uncontrolled manifold (UCM) method, the total joint angle variance was decomposed into two parts, the joint angle variance that did not affect the position of the end-effector (VUCM) and the variance that results in a deviation of the position of the end-effector from its mean (VORT). Analyses showed that some angles depended on length of the rod in use. For all rod lengths, VUCM was larger than VORT, and this did not differ over rod lengths, demonstrating that the arm was organized into a synergy. Finally, the variation in the joint angles in the arm as well as the degree of co-variation between these angles did not differ for the rod’s tip and the hand. We concluded that synergies are formed in the arm during reaching with an extended end-effector and those synergies stabilize different parts of the arm+rod system equally

Using curvature information in haptic shape perception of 3D objects

Are humans able to perceive the circularity of a cylinder that is grasped by the hand? This study presents the findings of an experiment in which cylinders with a circular cross-section had to be distinguished from cylinders with an elliptical cross-section. For comparison, the ability to distinguish a square cuboid from a rectangular cuboid was also investigated. Both elliptical and rectangular shapes can be characterized by the aspect ratio, but elliptical shapes also contain curvature information. We found that an elliptical shape with an aspect ratio of only 1.03 could be distinguished from a circular shape both in static and dynamic touch. However, for a rectangular shape, the aspect ratio needed to be about 1.11 for dynamic touch and 1.15 for static touch in order to be discernible from a square shape. We conclude that curvature information can be employed in a reliable and efficient manner in the perception of 3D shapes by touch

Embodying the mind and representing the body

Does the existence of body representations undermine the explanatory role of the body? Or do certain types of representation depend so closely upon the body that their involvement in a cognitive task implicates the body itself? In the introduction of this special issue we explore lines of tension and complement that might hold between the notions of embodiment and body representations, which remain too often neglected or obscure. To do so, we distinguish two conceptions of embodiment that either put weight on the explanatory role of the body itself or body representations. We further analyse how and to what extent body representations can be said to be embodied. Finally, we give an overview of the full volume articulated around foundational issues (How should we define the notion of embodiment? To what extent and in what sense is embodiment compatible with representationalism? To what extent and in what sense are sensorimotor approaches similar to behaviourism?) and their applications in several cognitive domains (perception, concepts, selfhood, social cognition)

Perception of limb orientation in the vertical plane depends on center of mass rather than inertial eigenvectors

We performed two experiments to test the hypothesis that the perception of limb orientation depends on inertial eigenvectors (

Grasping the changes seen in older adults when reaching for objects of varied texture.

Old age is associated with reduced mobility of the hand. To investigate age related decline when reaching-to-lift an object we used sophisticated kinematic apparatus to record reaches carried out by healthy older and younger participants. Three objects of different widths were placed at three different distances, with objects having either a high or low friction surface (i.e. rough or slippery). Older participants showed quantitative differences to their younger counterparts - movements were slower and peak speed did not scale with object distance. There were also qualitative differences with older adults showing a greater propensity to stop the hand and adjust finger position before lifting objects. The older participants particularly struggled to lift wide slippery objects, apparently due to an inability to manipulate their grasp to provide the level of precision necessary to functionally enclose the object. These data shed light on the nature of age related changes in reaching-to-grasp movements and establish a powerful technique for exploring how different product designs will impact on prehensile behavior